In many industrial applications it is necessary to divide a flow of materials into a number of equal, smaller flows. This is normally accomplished by utilizing volumetric metering screws. However, this method becomes useless when, because of various process requirements, the material is first processed and dewatered through a screw press or a plug feeder. Material passing through this equipment will drastically alter its density. That will result in uneven density, which volumetric metering screws cannot properly handle. Such operation is nowhere more important than in the refining of woodchips or other cellulosic material in a twin flow refiner, i.e. a refiner having one rotating rotor element between two stationary elements, thereby forming two grinding zones.
A twin flow refiner relies entirely on the mat of fibrous material being fed to each side of the rotating rotor element, where the grinding zones are contained. It is imperative to maintain the gaps of the two grinding zones within one-half thousandth of an inch, otherwise an inferior fiber quality will be produced. Although each stationary element forming a side of the gap of the grinding zones is individually controlled by a servo mechanism, the rotating rotor position is entirely dependent on the nature of the fibrous mat which is maintained continuously in the two grinding zones. Uneven flow of each zone will result in disastrous fiber quality problems.
The present invention concerns a device that will restore the homogeneous density of the wood chips and fibrous material after being processed and dewatered through the screw press or plug feeder and at the same time spread the material evenly into two or more metering screws. It has been found that this device provides improvement in fiber quality with superior paper tensile strength.